Metal gaskets for automobiles may require a saline spray test as a spec evaluation item, in preparation for situations in which the automobile runs in a seaside area or in an area in a cold region in which a snow melting agent is sprinkled. For example, in the case where electronic components such as an electronic control unit (ECU), a power control unit (PCU), an inverter, and a converter are stored inside a housing formed of two members of a case member and a lid member, the above-mentioned saline spray test may be performed in a state where a metal gasket seals abutting surfaces between the case member and the lid member.
In automobile components, iron-based or aluminum-based metal is mainly used as material for two members of, for example, a case member and a lid member. In the case of performing a saline spraying test, when a counter member contacting the metal gasket is formed of an aluminum material (including aluminum alloy, the same is applicable hereinafter) such as ADC12, the sprayed saline may adhere and stay in a space between the metal gasket and the abutting surfaces, and repeat drying and wetting, to cause corrosion (space corrosion) due to saline (difference in ion concentration) in the aluminum material. The metal gasket exhibits a sealing function by reaction force of the bead made in contact with the abutting surfaces, but the sealing function is lost when the corroded section pierces through the seal line (bead contact line) of the bead.
As measures against it, the applicant of the present application has presented a metal gasket having a structure in which a bent section (hereinafter referred to as “peripheral creased section”) to prevent infiltration of saline is formed over the entire perimeter of the gasket, the peripheral side of the space between the abutting surfaces is substantially filled with the peripheral creased section to reduce the space, preventing adhesion and stay of saline, and delaying loss of the sealing function due to saline (Patent Document 1).